Actual source code: ex12.c


  2: static char help[] = "Scatters from a sequential vector to a parallel vector.\n\
  3: This does case when we are merely selecting the local part of the\n\
  4: parallel vector.\n";

  6: #include <petscvec.h>

  8: int main(int argc,char **argv)
  9: {
 10:   PetscMPIInt    size,rank;
 11:   PetscInt       n = 5,i;
 12:   PetscScalar    value;
 13:   Vec            x,y;
 14:   IS             is1,is2;
 15:   VecScatter     ctx = 0;

 17:   PetscInitialize(&argc,&argv,(char*)0,help);

 19:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 20:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 22:   /* create two vectors */
 23:   VecCreate(PETSC_COMM_WORLD,&x);
 24:   VecSetSizes(x,PETSC_DECIDE,size*n);
 25:   VecSetFromOptions(x);
 26:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

 28:   /* create two index sets */
 29:   ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
 30:   ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);

 32:   /* each processor inserts the entire vector */
 33:   /* this is redundant but tests assembly */
 34:   for (i=0; i<n; i++) {
 35:     value = (PetscScalar) (i + 10*rank);
 36:     VecSetValues(y,1,&i,&value,INSERT_VALUES);
 37:   }
 38:   VecAssemblyBegin(y);
 39:   VecAssemblyEnd(y);

 41:   VecScatterCreate(y,is2,x,is1,&ctx);
 42:   VecScatterBegin(ctx,y,x,INSERT_VALUES,SCATTER_FORWARD);
 43:   VecScatterEnd(ctx,y,x,INSERT_VALUES,SCATTER_FORWARD);
 44:   VecScatterDestroy(&ctx);

 46:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 48:   VecDestroy(&x);
 49:   VecDestroy(&y);
 50:   ISDestroy(&is1);
 51:   ISDestroy(&is2);

 53:   PetscFinalize();
 54:   return 0;
 55: }

 57: /*TEST

 59:    test:
 60:       nsize: 2

 62: TEST*/